Royalty income from garage inventions

[megaptera]

Hello -

I've been in the US as a nonimmigrant alien on an academic visa.

I have a quite technical hobby, and I have had a "garage lab." Some of the knowledge I have acquired through my hobby is recognized by a manufacturer to be of their commercial interest, and they want to license my inventions, some with patents, some without, and they want to pay me a flat percentage royalty of the sales. The products are very similar to what I have invented for my own use to practice my hobby, and the company will manufacture, advertise, market, customer support, etc. My role is limited to send proprietary information by certified mail, and check my bank accounts.

My question is whether this royalty income is considered passive income. I do believe so, because I am not working for the company, but merely providing my knowledge. (I would make the same invention for my own use anyway, and most of them were made before the company contacted me.) However, I would like to see others' opinions and rationales before I proceed on this decision.

Thanks!